Microwave heating of radioactive waste material is a well known means for treating radioactive waste such that the resulting wasteform can be stored safely. Several earlier attempts at microwave energy treatment of waste material included devices with moving parts and bearings which were prone to wear and corrosion. Further, prior art treatment methods created glass or vitreous wasteforms which are sensitive to changes in waste feed chemical composition.
More recently, microwave energy treatment devices which utilize in-drum processing have been developed. In particular, U.S. Pat. Nos. 4,940,865 and 5,324,485 disclose devices where waste material is deposited into a container and microwave energy heats the waste material to a molten state. The waste material upon cooling solidifies into a wasteform which can be safely stored. The '865 patent utilizes a turntable for rotating a waste drum. The turntable is subject to failure thereby affecting the uniform heating of the waste. Moreover, neither patent addresses the problem of microwave leakage sufficiently. Also, the microwave energy transfer to the waste is not maximized.
Therefore, it is an object of the present invention to provide a microwave applicator and waste treatment method which provides a greater energy transfer efficiency than apparatus of the prior art.
It is another object of the present invention to provide a microwave applicator and waste treatment method wherein the final form defines a crystalline structure.
Further, it is an object of the present invention to provide a microwave applicator constructed in a manner such that the heat generated during the process is confined to a disposal container.
Moreover, it is an object of the present invention to provide a microwave applicator which is designed to minimize microwave leakage.
It is yet another object of the present invention to provide a microwave applicator which provides uniform heating and melting of the waste.
It is also an object of the present invention to provide a near-uniform heating of waste material in a rectangular configuration.
It is an object of the present invention to enable a waste solidification using microwave energy in a vessel of rectangular configuration and increasing the packing efficiency of the final waste form for disposal.